This canonical 4D implicit function propagates points across time and extracts the pixel-aligned visual representations from different frames.
This differs from:
1) prior works that only consider static objects.
Actually, setting \(N=1\)  in eq:define xp will simplify eq:implicit to \(g({\mathbf {p}}, f_\text{enc}(\psi ({\mathbf {p}}), I))\) , recovering a static Pixel-aligned Implicit Function (PIFu) used in [1]}, [2]};
2) OFlow [3]} which encodes the whole video clip \(\lbrace I_1, \dots , I_N\rbrace \)  into one single feature vector, thus loosing spatial information.
